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Old 10-09-2015, 04:23 AM   #1
cuzncletus
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Default rear radius rod placement

I'm sure this has been hashed out before but if I read it, it didn't sink in. I'm building an A-V8 using a 39 rear. Looking to see what others have done, I see a lot of people relocated their radius rods out to the frame. I'm doing this on the front based on the theory that the Ford front axle can twist slightly as it travels through an arc. The rear axle is obviously not going to do this. In my mind, it seems that in some extreme conditions on the suspension, such as hard cornering, is going to put a lot of stress on the radius rods or their mounting points.

I'm guessing locating the radius rods to the frame would be OK if one was using an open rear as the U-joints and yoke would allow some twist in the rear. But a torque tube ties the rear axle into a straight up and down movement. It seems that splitting the rear radius rods, some equipment is going to get torn up or someone is going to get hurt. Am I right or am I overthinking this?
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Old 10-09-2015, 05:51 AM   #2
JSeery
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Default Re: rear radius rod placement

In the past many Hot Rodders have split the rear wishbones as you describe. This does not work properly, also because of the reason you stated. It doesn't much matter if the rear axle is open driveshaft or enclosed, the axle will not twist and a lot of stress is placed on the radius rods, resulting in failure in time. The only way to get it to work is something similar to the original setup so that the radius rods move with the torque tube or incorporate a ball type of joint that allows the radius rods to rotate with the torque tube. As a side note, in addition to the side to side rotation we are talking about, with an open driveshaft there is also for and aft rotation. The stock radius rods can not handle this rotation (that is what the torque tube was for). Additional measures are required with an open rear axle such as one or more additional radius rods to control axle rotation. There has been a lot of discussion on this topic on the HAMB with various suggestions of solutions.
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Old 10-09-2015, 07:42 AM   #3
john in illinois
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Default Re: rear radius rod placement

I like buggy springs with center pivot axle, I always get good handling.
On my 39 axle in the AV8 I used 48 bones bent and lengthened to fit. I did not want to weld a lug on the torque tube and risk pulling out of alignment.

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Old 10-09-2015, 08:46 AM   #4
V8COOPMAN
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Default Re: rear radius rod placement

You haven't made it "clear as mud" yet whether or not you're going to continue to use a torque tube, but it sounds like you are. IF you are going to use a torque tube, I can't see any beneficial reason to split the radius rods.

On the contrary, ONE of the pitfalls to splitting the radius rods ('bones) while retaining the torque tube is that the two bones would have to be lengthened and mounted such that their up / down pivot points would have to be precisely on a horizontal line drawn through the center of the torque tube U-joint. If the two pivot points are mounted above, below, behind or forward of the U-joint center-line, any articulation of the rear end will be futile, not to mention immediately destructive. In short, the 'bones need to be structurally attached to the torque tube in a fashion similar to Henry's original design for the rear end movements to function correctly.

If in fact you are planning an OPEN drive rear end, there are different, workable alternatives. DD
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Old 10-09-2015, 09:00 AM   #5
Ralph Moore
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Default Re: rear radius rod placement

Quote:
Originally Posted by john in illinois View Post
I like buggy springs with center pivot axle, I always get good handling.
On my 39 axle in the AV8 I used 48 bones bent and lengthened to fit. I did not want to weld a lug on the torque tube and risk pulling out of alignment.

John
I did just the opposite, I took 37 rear bones and shortened them to match the 15 or so inches I had to remove to get the 37 torque tube to fit the 32 frame.
And if you've ever cut a torque tube in half, I wouldn't worry about twisting it by re welding a tab for the radius rods. These tubes are really stout. I've moved and re welded tabs with no movement of the tube.

And if your not getting rid of the torque tube, keep your bones where they belong.
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Old 10-09-2015, 09:50 AM   #6
Andy
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Default Re: rear radius rod placement

I saw car at a rod run that had the radius rods moved out to the sides of the frame. The rods had been welded to the axle. They had been over stressed and had peeled a section out of the axle tube. I put a finger down in the hole and could touch the axle shaft. The rod was still attached to the rear with the torn part making a hinge.
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Old 10-09-2015, 10:26 AM   #7
19Fordy
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Default Re: rear radius rod placement

I respectfully suggest that you really do a lot more research as to what is the safest way to split your wish bones. Here's a start: http://www.hotrod.com/how-to/1506-ti...-mounting-kit/ Also, call www.hotrodworks.com and get their input. What you do may seem to work for a while, but there is a tremendous amount of stress put on wishbones especially when they are split. Constant stress will lead to metal fatigue and eventual failure. Please read all of this thread:
http://www.jalopyjournal.com/forum/t...e-pics.579624/

However, pay attention to what V8Coopman says. Henry Ford did it correctly.

Last edited by 19Fordy; 10-10-2015 at 10:42 AM.
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